Effects of Asphalt Mixture Input on AASHTOWare Pavement Mechanistic-Empirical Design Analysis of Rehabilitated Pavements

Hot-Mix Asphalt (HMA) creep compliance is a primary mechanical property input for the AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software for design analysis of rehabilitated pavements. This study investigated the impact of the creep of HMA mixes with reclaimed asphalt pavement (RAP) on the performance of the HMA-overlaid pavements in Kansas. Hierarchical Level 1 inputs of creep compliance were obtained for two overlay mixtures by the AASHTO T 322–07 test method. Level 3 inputs were obtained as defaults in the PMED analysis software. Twenty-five asphalt concrete (AC) overlays over existing AC and 14 AC overlays over Jointed Plain Concrete Pavement (JPCP) were selected to make distress predictions using the AASHTOWare PMED software (version 6.2). The failure criteria for new asphalt pavements were used in PMED. The distresses predicted include roughness (in terms of the International Roughness Index, IRI), permanent deformation (rutting), AC total transverse cracking (thermal plus reflective), AC thermal cracking, AC fatigue cracking (both bottom-up and top-down), and JCPC transverse cracking in terms of percent slabs (AC overlay over JPCP only). The results show that mixtures with softer binders produced less thermal cracking for AC overlays on existing AC pavements. For AC overlays on existing JPCP, a mixture with a lower PG-grade binder eliminated thermal cracking on the AC overlays. For most projects, a softer binder also helped decrease the total transverse cracking.